Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R33/00—Arrangements or instruments for measuring magnetic variables
  • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
  • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
  • G01R33/48—NMR imaging systems
  • G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
  • G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R33/00—Arrangements or instruments for measuring magnetic variables
  • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
  • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
  • G01R33/48—NMR imaging systems
  • G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
  • G01R33/543—Control of the operation of the MR system, e.g. setting of acquisition parameters prior to or during MR data acquisition, dynamic shimming, use of one or more scout images for scan plane prescription
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R33/00—Arrangements or instruments for measuring magnetic variables
  • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
  • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
  • G01R33/48—NMR imaging systems
  • G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
  • G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
  • G01R33/565—Correction of image distortions, e.g. due to magnetic field inhomogeneities
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R33/00—Arrangements or instruments for measuring magnetic variables
  • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
  • G01R33/24—Arrangements or instruments for measuring magnetic variables involving magnetic resonance for measuring direction or magnitude of magnetic fields or magnetic flux
  • G01R33/243—Spatial mapping of the polarizing magnetic field
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R33/00—Arrangements or instruments for measuring magnetic variables
  • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
  • G01R33/24—Arrangements or instruments for measuring magnetic variables involving magnetic resonance for measuring direction or magnitude of magnetic fields or magnetic flux
  • G01R33/246—Spatial mapping of the RF magnetic field B1
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R33/00—Arrangements or instruments for measuring magnetic variables
  • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
  • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
  • G01R33/48—NMR imaging systems
  • G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
  • G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
  • G01R33/561—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution by reduction of the scanning time, i.e. fast acquiring systems, e.g. using echo-planar pulse sequences
  • G01R33/5611—Parallel magnetic resonance imaging, e.g. sensitivity encoding [SENSE], simultaneous acquisition of spatial harmonics [SMASH], unaliasing by Fourier encoding of the overlaps using the temporal dimension [UNFOLD], k-t-broad-use linear acquisition speed-up technique [k-t-BLAST], k-t-SENSE
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R33/00—Arrangements or instruments for measuring magnetic variables
  • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
  • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
  • G01R33/48—NMR imaging systems
  • G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
  • G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
  • G01R33/565—Correction of image distortions, e.g. due to magnetic field inhomogeneities
  • G01R33/56509—Correction of image distortions, e.g. due to magnetic field inhomogeneities due to motion, displacement or flow, e.g. gradient moment nulling

Definitions

• MR Magnetic Resonance
• MRI magnetic resonance imaging
• MRS magnetic resonance spectroscopy
• Magnetic Resonance Imaging uses a pre-scan to calibrate and create initial references before each scan sequence.
• a typical pre-scan includes a coil survey, a sense reference, a BO mapping, and a Bl mapping.
• a coil survey typically lasts more than 10 seconds.
• a sense reference typically lasts more than 10 seconds.
• a B0 mapping lasts more than 15 seconds, and a Bl mapping lasts between 15 and 30 seconds.
• the total pre- scan can last longer than one minute. If the coil or the patient position change, then the information is inaccurate. Ideally, all of these pre-scans need be repeated. Otherwise, the reconstructed image may contain serious artefacts. However, the repetition of these reference scans prolong the total acquisition time.
• the pre-scan is usually run at a low resolution to save time. If the coil elements are small, a low resolution image may not provide sufficiently accurate coil sensitivity maps. A lack of sufficiently accurate coil sensitivity maps result in residual aliasing artefacts in SENSE images.
• a typical imaging subject is scanned with an average of 4 or more imaging sequences.
• the imaging sequences are typically performed on the same region of interest but focus on different aspects of the subject anatomy, achieve different contrasts, and the like. Since the same subject is scanned in the same system using the same RF coil, the information such as B0, ⁇ ⁇ ⁇ , optimized acquisition trajectory and reconstruction parameters, etc, can be shared among these scans for different contrasts to improve the image quality.
• the present application provides a new and improved MR imaging using shared information which overcomes the above-referenced problems and others using one set of pre-scans.
• a magnetic resonance method in which a pre-scan sequence is followed by a plurality of scanning sequences without pre- scan sequences in between and in which information of the pre-scan sequence is refined by each scan sequence.
• a magnetic resonance system includes a magnet which generates a BO field in an examination region, a gradient coil system which creates magnetic gradients in the examination region, and an RF system which induces resonance in and receives resonance signals from a subject in the examination region.
• the system further includes one or more processors which are programmed to control the RF and gradient coil systems to perform a pre-scan sequence to generate pre-scan data.
• the pre-scan data is processed to create pre-scan information.
• the RF system and the gradient coil system are controlled to use the pre-scan information to perform a first sequence to generate first sequence data, as well as refined pre-scan data.
• the one or more processors controls at least one of the RF and gradient coil systems using the refined pre-scan data to perform a second sequence to generate second sequence data and/or reconstruction of the second sequence data into an image representation using refined pre-scan information.
• a magnetic resonance method includes performing a magnetic resonance pre-scan sequence to generate pre-scan information, performing a first sequence to generate first sequence data, and refining the pre-scan information with the first sequence data to create refined pre-scan information.
• a second scan sequence is performed to generate second scan data and at least one of the second scan sequence is reconstructed using the refined pre-scan information and/or the refined pre-scan sequence information is used when performing the second scan sequence.
• a magnetic resonance method in which an RF and gradient coil system are controlled to perform a pre-scan sequence to generate pre-scan information and perform a first imaging sequence to generate first image sequence data.
• the first image data is reconstructed using the pre-scan information to generate a first image representation.
• the first imaging sequence data is used to refine the pre-scan information.
• the RF and gradient coil systems are controlled to perform a second imaging sequence to generate second imaging data.
• the second imaging sequence data are reconstructed using the refined pre-scan information to generate a second image representation.
• One advantage is that total time for a subject in a scanner is reduced. Another advantage is that pre-scans between sequences due to patient or coil motion are reduced or eliminated.
• Another advantage is that the order of scans can be optimized.
• Another advantage resides in correcting motion across imaging sequences.
• Another advantage resides in accelerating individual sequences using a priori information.
• Another advantage is that the accuracy of pre-scan information and reconstructed images are improved.
• Another advantage resides in avoiding mis-registration due to motion.
• Another advantage resides in replacing corrupted data with uncorrupted data.
• Another advantage is that the information from prior images guides the sampling trajectory.
• Another advantage is that the parameters used in reconstruction can be optimized using prior images.
• the invention may take form in various components and arrangements of components, and in various steps and arrangements of steps.
• the drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention.
• FIGURE 1 is a diagrammatic illustration of a magnetic resonance imaging system in accordance with the present invention.
• FIGURES 2A and 2B illustrate the difference between a typical subject imaging sequence (FIGURE 2A) and an embodiment of the present application (FIGURE 2B).
• FIGURE 3 illustrates sharing data stores.
• FIGURE 4 illustrates imaging sequences ordered to optimize the pre-scan of information for subsequent imaging sequences.
• FIGURE 5 illustrates images from embodiments of the process technique.
• a magnetic resonance imaging system includes a magnet 10 which generates a static Bo field in an examination region 12.
• One or more gradient magnetic field magnets 14 generate magnetic field gradients across the Bo field in the imaging region.
• Radio frequency coils or elements 16 generate Bi RF pulses for exciting and manipulating magnetic resonance and induce magnetic resonance signals.
• whole body transmit and receive RF coils it is to be appreciated that separate RF coils can be provided for transmitting and receiving and that the receive and/or the transmit coils may be local coils, whole body coils, or a combination of the two.
• C-type or open magnetic resonance systems are also contemplated.
• One or more RF transmitters 18 apply RF signals to the radio frequency coils to cause the Bi pulses to be applied in the examination region.
• One or more receivers 20 receive the magnetic and demodulate the magnetic resonance signals received by the RF coils 16.
• a gradient controller 22 controls the gradient coil 14 to apply the gradient magnetic field pulses across the examination region, commonly a combination of orthogonal gradients denoted as x, y, and z gradients.
• One or more processors 30 include a sequence controller 32 such as a sequence control computer algorithm, a sequence control module, or the like. As explained in greater detail below, the sequence controller 32 controls the one or more RF transmitters 18, the gradient controller 22, and the one or more RF receivers 20 to conduct a pre-scan magnetic resonance sequence followed by a plurality of different magnetic resonance sequences, such as a Ti weighted imaging sequence, a T 2 weighted imaging sequence, a diffusion weighted imaging sequence, or the like. The magnetic resonance signals from the pre-scan sequence are stored in a pre-scan data or information buffer 34.
• the one or more processors 30 includes the pre-scan information system 36 which derives pre-scan information from the pre-scan data, such as coil sensitivity maps, a Bo map, a Bi map, and the like as is explained in greater detail below.
• the sequence controller 32 uses the pre-scan information to adjust the parameters of the first imaging sequence and controls the RF transmitter, RF receivers, and the gradient controller 22 to generate the first imaging sequence which is stored in a k- space data memory 40.
• the one or more processors 30 further include a reconstruction module, series of program instructions, ASICs or the like.
• the reconstruction processor 12 reconstructs the first scan data from the k-space memory 40 into a first image representation which is stored in a first image memory 44 . The reconstruction is performed using the pre-scan information from the pre-scan information system 36.
• the pre-scan information system uses the first scan data from the k-space memory 40 and data from the reconstructed image from the first image memory 44i to update, refine, and improve the accuracy of the pre-scan information.
• the sequence controller 32 uses the improved pre-scan information to conduct the second imaging scan which is reconstructed into a second image representation that is stored in a second image representation memory 44 2 .
• the pre-scan information system 36 again updates, improves, and makes the pre-scan information more accurate. This process is repeated generating the third and subsequent images in the sequence with the pre-scan information being updated, improved, and rendered more accurate before each subsequent scan sequence.
• k-space or image data from earlier sequences can be used by the reconstruction processor to accelerate or refine the images of later sequences.
• FIGURE 2A a set of four-scan sequences is diagrammed for logical comparison with the method which is the subject of this application in FIGURE 2B.
• each scan sequence was run independently. Each scan sequence commences by sharing one pre-scan sequence 50 unless motion happens. Most scans in one protocol included the same information for the same patient for the same session, and typically scan the same region of interest for different contrasts.
• the pre- scan sequences between imaging sequences are eliminated and the imaging sequences are run consecutively following a single pre-scan sequence 50. Individual sequences may run in reduced in the amount of time, or performed with an accelerated method by sharing data from one image sequence to the next. In addition, the ordering of the sequences may be altered to reduce the overall scan time.
• FIGURE 2B shows the re-ordered set of sequences which move the second imaging sequence to last.
• the dotted lines across the imaging sequences indicate a reduction in scan time or acceleration due to use of common information stores from the pre-scan or prior scan sequences.
• steps 200 and data stores 210 of an MRI embodiment are diagrammed.
• pre-scan data is generated from which pre-scan information is generated.
• the pre-scan information includes initial Radio Frequency (RF) coil sensitivity maps 100 are created.
• a SENSE reference 110 may be created.
• Initial Bo maps 120 and Bi maps 130 are created.
• the RF coil sensitivity maps 100, SENSE reference 110, calibration signal, phantom references, B 0 120, and/or Bi maps 130 are information generated and used during the pre-scan sequence 50.
• This initial pre- scan information is used for a first imaging sequence 60.
• the pre-scan information storage may involve files or data structures.
• the accuracy depends upon the lack of motion of the subject, the resolution with which it is created, and the like.
• the pre-scan sequence 50 is run at a low resolution.
• the pre-scan sequence 50 is used primarily to calibrate with the actual patient load using the selected whole body or local RF coil(s).
• the initial pre-scan information from the pre-scan sequence 50 is updated with more accurate pre-scan information 100', 110', 120', 130'. Additional pre-scan information may be generated which enhances the image quality.
• the additional information includes periodic motion information 140, image references 150, and/or anatomical landmarks or segments 160.
• Various techniques are used to improve image quality, accuracy, and contrasts.
• the first image scan sequence functions both to generate a first image representation, but also as a pre-scan for a second imaging sequence.
• the resulting imaging data is saved as a reconstructed image and/or saved as intermediate data for later image reconstruction.
• a next imaging sequence 70 is started, unlike the prior art, no pre-scan is conducted. Rather, the revised pre-scan information is used instead.
• the sequences 200 are re-ordered to optimize the data stores 210 that can be used in the subsequent imaging sequence(s).
• Several of the data stores 210 are created in the pre-scan 100, 110, 120, 130. More are added from the first imaging sequence 140, 150, 160, 170, 180. Additional data stores include subject motion references 140, full or partial k-space data, specific time frames, automated calibration signal references, anatomic landmarks or segments references 150, and other motion detection/correction references 160.
• the first imaging sequence 60 also revises the data stores 100', 110', 120', 130' from the pre-scan. File structures and databases may be added for performance, searching, and/or each of use.
• the data stores 210 exist beyond the life of the individual imaging sequence.
• These data stores 210 are then used as input to the next imaging sequence 70 data collection, or its image reconstruction. Where creating data stores 210 is performed in either a pre-scan 50 or earlier imaging sequence, later sequences either use or revise the data stores. New data stores are added when new information becomes available. When motion corrupts data collection, prior data stores are used to correct, replace, or refresh the motion corrupted data. The accuracy of image registration is measured and tracked between the different imaging sequences which avoid misregistration. The data stores 210 are again updated 100", 110", 120", 130", 140', 150', 160', 170', 180' using data from the second imaging sequence 70.
• a radio frequency coil sensitivity map 100', optimized acquisition trajectory 180, and optimized reconstruction parameter 170 from a first imaging sequence is updated to improve the accuracy for a later parallel imaging sequence.
• Another embodiment uses an updated Bo map 120" improves a geometry distortion correction for a later echo planar imaging sequence.
• the first imaging sequence 60 is a Tl weighted imaging sequence with an acceleration factor of 2.
• the second imaging sequence 70 is a T2 sequence with an acceleration factor of 5.
• the RF coil sensitivity map 100 is initially created in the pre-scan 50 and placed in a data store 210.
• the Tl imaging sequence 60 uses and revises the RF coil sensitivity map 100' in the data store which is then preserved and used in the T2 imaging sequence 70.
• the T2 imaging sequence 70 can be run faster due to the more accurate and complete RF coil sensitivity map 100', optimized acquisition trajectory 180, and optimized reconstruction parameter 170 created with the Tl imaging sequence 60.
• the T2 images are reconstructed using RF coil sensitivity map 100'.
• the Tl image is used to identify the region of the k-space which is of primary interest.
• the sequence controller can tailor the k-space directory accordingly, e.g., to sample the region of primary interest more heavily.
• a priori information 190 can be manually input or received from other sources.
• the a priori information can be from prior imaging sessions, hospital database records, manual inputs, other diagnostic equipment, and the like.
• Subfigure (a) shows the low resolution sensitivity map of channel 4 calculated using pre-scan data.
• Sub figures (e) and (f) show the revised sensitivity map and optimized acquisition trajectory using (b).
• Sub figures (c) and (d) show the reconstructed T2w image (c) and the corresponding error map (d) using low resolution sensitivity map (a).
• Subfigures (g) and (h) show the reconstructed T2w image (g) and the corresponding error map (h) using high resolution sensitivity map (e), optimized acquisition trajectory (f), and reconstruction parameters generated using (b).
• the changes in methodology may be implemented through changes in software.
• the changes in software are reflected in the user interface where an operator selects the imaging sequences and then the software orders the sequences.
• the imaging station serves as the user interface or an alternative processor may be used.

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• High Energy & Nuclear Physics (AREA)
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• 2012
  • 2012-10-10 JP JP2014536368A patent/JP2014530080A/ja active Pending
  • 2012-10-10 IN IN2547CHN2014 patent/IN2014CN02547A/en unknown
  • 2012-10-10 EP EP12791256.6A patent/EP2751586A2/en not_active Withdrawn
  • 2012-10-10 RU RU2014119867/28A patent/RU2014119867A/ru not_active Application Discontinuation
  • 2012-10-10 BR BR112014009133A patent/BR112014009133A8/pt not_active Application Discontinuation
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  • 2012-10-10 WO PCT/IB2012/055471 patent/WO2013057629A2/en active Application Filing
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